What would be really cool is using every button several times over. (I actually wanted to do something kinda like that. Every button except the directional buttons.)Clearly the solution is to switch between each one. Just enable and disable each one like 60 times a second! (I know nothing.)

I'm still planning to have fully customizable controls so if you want to play the game with everything mapped to combinations, be my guest

The audio problem is that you don't want sounds playing twice. Instead for each sound you determine the closest/highest priority player and play it based off that distance and angle data.